Precipitation modes over the Western Ghats orography during the summer monsoon season

2021 ◽  
Author(s):  
Jayesh Phadtare ◽  
Jennifer Fletcher ◽  
Andrew Ross ◽  
Andy Turner ◽  
Thorwald Stein ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
West Coast ◽  
Western Ghats ◽  
Monsoon Season ◽  
Radiosonde Data ◽  
Summer Monsoon Season ◽  
The West ◽  
Radiosonde Station ◽  
Westerly Flow ◽  
The Western Ghats

<p>Precipitation distribution around an orographic barrier is controlled by the Froude Number (Fr) of the impinging flow. Fr is essentially a ratio of kinetic energy and stratification of winds around the orography. For Fr > 1 (Fr <1), the flow is unblocked (blocked) and precipitation occurs over the mountain peaks and the lee region (upwind region). While idealized modelling studies have robustly established this relationship, its widespread real-world application is hampered by the dearth of relevant observations. Nevertheless, the data collected in the field campaigns give us an opportunity to explore this relationship and provide a testbed for numerical models. A realistic distribution of precipitation over a mountainous region in these models is necessary for flash-flood and landslide forecasting. The Western Ghats region is a classic example where the orographically induced precipitation leads to floods and landslides during the summer monsoon season. In the recent INCOMPASS field campaign, it was shown that the precipitation over the west coast of India occurred in alternate offshore and onshore phases. The Western Ghats received precipitation predominantly during the onshore phase which was characterized by a stronger westerly flow. Here, using the radiosonde data from a station over the Indian west coast and IMERG precipitation product, we show that climatologically, these phases can be mapped over an Fr-based classification of the monsoonal westerly flow. Classifying the flow as 'High Fr' (Fr >1), 'Moderate Fr' ( 0.5 < Fr ≤ 1) and 'Low Fr' ( Fr ≤ 0.5 ) gives three topographical modes of precipitation -- 'Orographic', 'Coastal' and 'Offshore', respectively.  Moreover, these modes are not sensitive to the choice of radiosonde station over the west coast.</p>

Two Notes on Ptolemy's Geography of India

1941 ◽  
Vol 73 (3) ◽  
pp. 208-222 ◽  
Author(s):  
E. H. Johnston
Keyword(s):  
West Coast ◽  
Western Ghats ◽  
The West ◽  
Market Town ◽  
The City ◽  
The Town ◽  
Good Access ◽  
The Western Ghats ◽  
Market Towns

The Periplus Marts Erythræ describes the seaports below Barygaza in the following way according to Schoff's translation: “The market-towns of this region are, in order, after Barygaza: Suppara, and the city of Calliena, which in the time of the elder Saraganus became a lawful market-town; but since it came into the possession of Sandares [an unjustified conjecture for the text's Sandanes] the port is much obstructed, and Greek ships landing there may chance to be taken to Barygaza under guard. Beyond Calliena there are other market-towns of this region; Semylla.…” Suppara is now Sopara on the coast above Bassein, Semylla is Cemūla of two inscriptions, now Chaul, and Calliena is Kalyāṇa. This last, situated at the foot of the two regular ascents of the Western Ghats leading towards Nasik and Poona respectively and with good access to the sea, was the natural outlet for the commerce of the Andhra dominions on the west coast, and the notice, just quoted, shows how its trade was stifled, as the Kṣaharātas extended their rule southwards from Broach. It is unnecessary here to consider who are the kings alluded to in this passage or in the earlier one mentioning Nambanus (a conjecture for the text's Mambarus), but clearly we are dealing with the rivalry of the Western Satraps and the Andhra kings. That the former were successful in their policy towards Kalyāṇa is shown by Ptolemy's omission of the town. The order he gives (taking Renou's text) is Souppara mouth of the River Goaris, Dounga, mouth of the River Bêndas, Semyla.

An Unidentified Territory of Southern India

1922 ◽  
Vol 54 (2) ◽  
pp. 161-175
Author(s):  
K. V. Subrahmanya Aiyer
Keyword(s):  
West Coast ◽  
Western Ghats ◽  
Eleventh Century ◽  
Southern India ◽  
The South ◽  
The West ◽  
Conservative Nature ◽  
The People ◽  
The Western Ghats

Free intercourse with Malabar was long denied to the rest of Southern India by the formidable natural obstacle of the Western Ghats with their impenetrable fastnesses and few passes. Owing chiefly to this circumstance that part of the country remained to a great extent isolated and secure from frequent invasions by other southern powers. This isolation, coupled with the conservative nature of the people of this tract, accounts for the preservation intact of several ancient customs of the Indians. Even in later times, whenever there had been any general disaster affecting the whole of the Dekhan, such as an invasion by the Muhammadan kings of the Khilji and Taghlak lines, the west coast afforded a safe asylum to the rest of the south. There is nothing unnatural in the following exclamation of the poet-composer of the Tiruvālaṅgāḍu plates of the eleventh century a.d.:—“Excepting Paramēśvara, who else in this world could contemplate even in mind the humiliation of that country which is protected by the glory of the crest jewel of the Bhrgu race (i.e. Paraśu-Rāma) and the austerities of its chiefs, and which had not been injured by enemies.”

scholarly journals Does the Western-Ghats play any dynamical role in the distance effect of vortex over the Bay of Bengal on the enhancement of monsoon rainfall over Pune?

MAUSAM ◽  
2021 ◽  
Vol 57 (4) ◽  
pp. 567-578
Author(s):  
SOMENATH DUTTA ◽  
S. I. LASKAR ◽  
M. MAITI
Keyword(s):  
Bay Of Bengal ◽  
West Coast ◽  
Western Ghats ◽  
Monsoon Season ◽  
Distance Effect ◽  
Southwest Monsoon ◽  
The Other ◽  
Dynamical Model ◽  
Considerable Depth ◽  
The Western Ghats

lkj & bl ’kks/k i= esa nf{k.k&if’pe ekulwu _rq ¼,l-MCY;w-,e-,l-½ ds nkSjku caxky dh [kkM++h esa mBs coaMj ds nwjorhZ izHkko ds QyLo:Ik iq.ks esa o"kkZ esa gqbZ o`f) esa if’peh ?kkV ¼MCY;w-th-½ dh xR;kRed Hkwfedk ¼;fn dksbZ gks rks½ dh tk¡p djus dk iz;kl fd;k x;k gSA bldh tk¡p djus ds fy, e/; ekiØe vojks/k ds Åij ok;q&izokg ds ,d xR;kRed ekWMy dk mi;ksx fd;k x;k gSA N% ?kVukvksa ds v/;;u ls ;g Kkr gqvk gS fd caxky dh [kkM+h esa coaMj mBus dh fLFkfr esa iq.ks esa gqbZ o"kkZ esa o`f) ns[kh xbZ gSA bu N% ?kVukvksa esa ls pkj  ?kVukvksa esa ;g ns[kk x;k gS fd xR;kRed ekWMy iq.ks esa o"kkZ dh izsf{kr ?kV&c<+ ¼deh&cs’kh½ dk irk yxkus esa xq.kkRed :Ik ls lQy jgk gSA bu pkjksa ?kVukvksa esa if’peh iousa if’pe rV ds fdukjs m/okZ/kj esa vis{kkÑr dkQh rhoz FkhaA vU; nks ?kVukvksa esa ls ,d ?kVuk esa ;g ekWMy o"kkZ dh vf/kdrk dks] de ls de xq.kkRed :Ik esa] irk yxkus esa lQy jgk gS ijUrq o"kkZ esa deh dk irk yxkus esa vlQy jgk gSA ,d vU; ?kVuk esa ;g ekWMy iq.ks esa o"kkZ dh ?kV&c<+ Kkr djus esa xq.kkRed :Ik ls Hkh iw.kZr;k vlQy jgk gSA vafre nks ?kVukvksa esa if’pe rVh; LVs’ku ij if’peh iou detksj ,oa lrgh FkhA   An attempt has been made to examine the dynamical role (if any) played by the Western Ghats (WG), in the distance effect of vortex over the Bay of Bengal (BOB) on the rainfall enhancement over Pune, during southwest monsoon season (SWMS). To examine it, a dynamical model of airflow over a meso-scale barrier has been used. Six cases have been studied, in which enhancement of rainfall over Pune in presence of vortex over the Head Bay are noticed. Out of these six cases, in four cases it is found that the dynamical model can capture, at least qualitatively, the observed fluctuation (rise and fall) of rainfall over Pune. In these four cases westerly along west coast was strong with considerable depth in vertical. In one of the other two cases, the model has been able to capture, at least qualitatively, the observed rise in rainfall but failed to capture the observed fall in rainfall. In the other case the model has failed completely to capture, even qualitatively, the fluctuation in observed rainfall over Pune. In the last two cases, westerly along west coast station was weak and shallow.  

scholarly journals Geasters in the Western Ghats and west coast of India

2014 ◽  
Vol 1 (1) ◽  
pp. 207-219 ◽  
Author(s):  
Namera C. Karun ◽  
Kandikere R. Sridhar
Keyword(s):  
West Coast ◽  
Western Ghats ◽  
Economic Value ◽  
First Record ◽  
The West ◽  
West Coast Of India ◽  
Western Ghats Of India ◽  
Native Tree ◽  
Terminalia Paniculata ◽  
The Western Ghats

Inventory in different locations of the Western Ghats and west coast of India during 2011–2013 yielded six species of geasters (<em>Geastrum fimbriatum</em>, <em>G. lageniforme</em>, <em>G. pseudostriatum</em>, <em>G. saccatum</em>, <em>G. schweinitzii</em> and <em>G. triplex</em>). Based on fresh basidiomata, illustrations of geasters are presented with macroscopic and microscopic observations. Fruit bodies of <em>G. lageniforme</em> were gregarious and abundant followed by <em>G. triplex</em>, while <em>G. pseudostriatum</em> were rare and solitary. Among the geasters, <em>G. triplex</em> was ectomycorrhizal with native tree <em>Terminalia paniculata</em> of the west coast. <em>Geastrum fimbriatum</em>, <em>G. pseudostriatum</em> and <em>G. schweinitzii</em> constitute the first record for the Western Ghats of India. Distribution, substrate preference, ectomycorrhizal features, economic value and conservation of geasters are discussed.

scholarly journals Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: Ship-borne measurements and model simulations

2016 ◽  
Author(s):  
Imran A. Girach ◽  
Narendra Ojha ◽  
Prabha R. Nair ◽  
Andrea Pozzer ◽  
Yogesh K. Tiwari ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Surface Ozone ◽  
Ozone Production ◽  
Spatial And Temporal Variability ◽  
Summer Monsoon Season ◽  
Rainfall Events ◽  
Model Simulations ◽  
Mixing Ratios

Abstract. We present ship-borne measurements of surface ozone, carbon monoxide and methane over the Bay of Bengal (BoB), the first time such measurements have been taken during the summer monsoon season, as a part of the Continental Tropical Convergence Zone (CTCZ) experiment during 2009. O3, CO, and CH4 mixing ratios exhibited significant spatial and temporal variability in the ranges of 8–54 nmol mol−1, 50–200 nmol mol−1, and 1.57–2.15 µmol mol−1, with means of 29.7 ± 6.8 nmol mol−1, 96 ± 25 nmol mol−1, and 1.83 ± 0.14 µmol mol−1, respectively. The average mixing ratios of trace gases over northern BoB (O3: 30 ± 7 nmol mol−1, CO: 95 ± 25 nmol mol−1, CH4: 1.86 ± 0.12 µmol mol−1), in airmasses from northern or central India, did not differ much from those over central BoB (O3: 27 ± 5 nmol mol−1, CO: 101 ± 27 nmol mol−1, CH4: 1.72 ± 0.14 µmol mol−1), in airmasses from southern India. Spatial variability is observed to be most significant for CH4. The ship-based observations, in conjunction with backward air trajectories and ground-based measurements over the Indian region, are analyzed to estimate a net ozone production of 1.5–4 nmol mol−1 day−1 in the outflow. Ozone mixing ratios over the BoB showed large reductions (by ~ 20 nmol mol−1) during four rainfall events. Temporal changes in the meteorological parameters, in conjunction with ozone vertical profiles, indicate that these low ozone events are associated with downdrafts of free-tropospheric ozone-poor airmasses. While the observed variations in O3 and CO are successfully reproduced using the Weather Research and Forecasting model with Chemistry (WRF-Chem), this model overestimates mean concentrations by about 20 %, generally overestimating O3 mixing ratios during the rainfall events. Analysis of the chemical tendencies from model simulations for a low-O3 event on August 10, 2009, captured successfully by the model, shows the key role of horizontal advection in rapidly transporting ozone-rich airmasses across the BoB. Our study fills a gap in the availability of trace gas measurements over the BoB, and when combined with data from previous campaigns, reveals large seasonal amplitude (~ 39 and ~ 207 nmol mol−1 for O3 and CO, respectively) over the northern BoB.

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